1. Field of the Invention
The present invention relates to a novel electric potential mapping and electrode attachment device used to locate and map the HIS bundle electrical impulse section of the heart or any other cavity within the body and produce a high-quality electrocardiogram of the HIS bundle or other cavity with continuous electrical readings through cavity mapping, electrode attachment, final implantation into the patient, and programming of the pacemaker device.
2. Description of Related Art
The contractions of the atria and ventricles of a heart are synchronized for efficient pumping of blood through the body. An electrical impulse created by the sinus node is conducted to the ventricles by a specialized conduction system, referred to as the His bundle and His Purkinje system. The bundle of His, also known as the AV bundle or atrioventricular bundle, is a collection of heart muscle cells specialized for electrical conduction that transmits electrical impulses from the AV node (located between the atria and the ventricles) to the point of apex of the fascicular branches. The fascicular branches then lead to the Purkinje fibers which innervate the ventricles, causing the cardiac muscle of the ventricles to contract at a paced interval. The His bundle is responsible for rapid sequential multi-site activation of the ventricle which results in efficient simultaneous contraction of both heart ventricles.
At times, an external device, such as an artificial pacemaker, is connected to the heart for activation of the myocardium. The impulse is carried through a set of electric wires (leads) to the electrode placed on or in the heart. The most common position of these electrodes is the right ventricular apex. The electrical stimulus causes the heart muscle to contract. This can be seen in U.S. Pat. No. 5,902,324 “Bi-Atrial and Bi-Ventricular Sequential Cardiac Pacing Systems” Thompson et al. issued May 11, 1999, (Thompson).
It has been determined that stimulation and pacing are more efficient if the His bundle system is stimulated instead of the heart muscle. This has been described in “Permanent, Direct His-Bundle Pacing—A Novel Approach to Cardiac Pacing in Patients With Normal His-Purkinje Activation”, Pramod Deshmukh, MD, David A. Casavant, MS, Mary Romanyshyn, CRNP, Kathleen Anderson, BSN, Oct. 1, 1999, cardiology Div., Robert Packard Hospital, Sayre, Pa. and Medtronic, inc. Minneapolis, Minn., © 2000 American Heart institute, (Deshmukh). This paper indicated that the right ventricular (RV) apical pacing caused abnormal contraction of the ventricles had disadvantageous effects on cardiac efficiency. RV pacing has also been associated with changes that cause the left ventricular function to deteriorate, “Long-Term His-Bundle Pacing and Cardiac Function” by Melvin M. Scheinman, MD, Leslie A. Saxon, MD, Dept. of Medicine, Univ. of California, San Francisco, © 2000 American Heart Association, Inc., (Scheinman). Scheinman supports and reiterates the findings of Deshmukh.
The process of mapping the HIS bundle and attaching the electrode to a precise location in the HIS bundle is currently an extremely difficult surgical procedure because the HIS bundle is very small and is located inside of a small heart chamber in blind corner location that is very difficult to get to laproscopically. This can be seen in U.S. Pat. No. 6,937,897 B2 “Electrode for HIS Bundle Stimulation”, Min et al. issued Aug. 30, 2005, The location and attachment process can become more difficult since the heart is beating and the location of the HIS bundle changes throughout the beating cycle. The heart ‘torques’ when it beats so it translates and rotates as it expands and contracts. In addition, the current means of accessing the HIS bundle is by passing a catheter through the superior vena cava into the atrium and placing it against the atrium wall, so all positioning must be done remotely by manipulating a catheter from outside of the patient.
Note that this invention is very suitable for application and mapping of other body cavities. The HIS bundle is very small and is located in a very hard to reach area. Because of the high degree of control required to effectively map this cavity, the device may be easily used to map practically any other body cavity in humans or animals.
Pacemaker electrodes are attached to heart tissue by screw means. A screw is a helix or a corkscrew-shaped appendage attached to the distal end of the electrode, with its longitudinal axis normal to the distal outer surface of the electrode, where the helix is used to literally screw into heart tissue or otherwise attach or seat the distal outer surface of the electrode onto heart tissue at a precise point. Electrodes typically use a fixed screw or a rotational screw design. With fixed screw electrodes, the helix is fixed onto the distal outer surface of the electrode. Thus, the whole electrode must be rotated to rotate the helix and attach the electrode to the heart. With rotational screw electrodes, the helix may be rotated in isolation, without also rotating of the electrode. With rotational screw, the helix is fixed to a holder, where the holder may be rotated, causing the helix to rotate and extent distally from the distal outer surface of the electrode, thereby extending the screw from such and attaching to heart tissue. The distal surface of the electrode has a hole or aperture from which the helix extends and retracts.
Mapping is the process of positioning the electrode, recording an electrical potential reading, repositioning the electrode, recording another electrical signal, and repeating until an accurate enough map or sufficient amount of electrical readings is taken by the surgeon to render an electrical topography of the heart chamber or otherwise enough information to determine the exact best position on the His bundle to attach the electrode in order to stimulate the simultaneous contraction of both ventricles to achieve maximum pumping efficiency. The electrical potential reading used in the mapping process is the electric potential difference between the electrode collar and the electrode helix, as set forth in Deshmukh. The electrode collar is located on the distal outer surface of the electrode. The electrode collar is typically the outer ring on the distal outer surface of the electrode. In the case of rotational screw electrodes, typically, the helix extends from the center of the ring of electrode collar.
With prior art methods and devices, after the surgeon determines the precise optimum attachment point, he must disconnect one or both electrical signals/readings in order to begin and complete the rotating of the electrode or helix. At this point, the electrode may move slightly off-center, in any direction, from its precise location. A fraction of a millimeter shift could substantially change electrical readings.
Such mislocations are typically discovered after attachment, when the surgeon re-connects electrical signals to see that the electrical readings have changed. At this point, the surgeon must: disconnect electrical signals, retract the electrode or helix, reconnect electrical signals, remap, relocated electrode, disconnect electrical signals, reattach electrode to heart, reconnect electrical signals, and recheck electrical signals, perhaps only to repeat this procedure over and over again. This could theoretically lead to an endless cycle or infinite loop of mislocations.
To solve this problem, this invention provides continuous electrical signal monitoring of the heart as the electrode is moved within the heart and rotated for attachment means into heart tissue. Thus, if the electrode were to move off-center from the precise location determined by electrical signal readings, then the surgeon would immediately know, discontinue attachment, unscrew the electrode or helix, and make adjustments or otherwise relocate to offset the effect, and begin attachment again. Electrical signals are also continuously monitored after attachment. The surgeon can be certain of accurate and precise electrode placement. The method of attachment disclosed here allows more exact control and placement of the electrode because of the superior amount of measurement data produced by electric potential mapping and electrode attachment device.
Additionally, electric potential mapping and electrode attachment device can provide a complete and uninterrupted electrocardiogram of the HIS bundle. The surgeon has continuous electric potential readings right up to final disconnection of the attachment device and attachment of the pacemaker control module for final insertion into the patient. This data is necessary as set forth in Deshmukh to program the pacemaker “to pace” the heart most efficiently. Electric potential mapping and electrode attachment device is first to provide such a cardiogram of the HIS bundle during rotation and attachment as well as before and after. This data better ensures that the pacemaker will be programmed to run in the most efficient fashion because the cardiogram used for input in the programming is more exact, without disconnection of electrical contacts, ending of one cardiogram, only to start a new one after electrode attachment. With the prior art, it would be possible to use a cardiogram generated from a different location, where the electrode move off-center slightly during attachment. This would yield improper programming of the pacemaker, so it would not pace the heart in the most efficient fashion.